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The ODINUS Mission Concept The Scientific Case for a Mission to the Ice Giant Planets with Twin Spacecraft to Unveil the History of our Solar System Spokeperson: Diego Turrini Istituto di Astrofisica e Planetologia Spaziali INAF-IAPS Via del Fosso del Cavaliere 100 00133 - Rome, Italy Email: [email protected] The ODINUS Mission Concept Authors list Diego Turrini1, Romolo Politi1, Roberto Peron1, Davide Grassi1, Christina Plainaki1, Mauro Barbieri2, David M. Lucchesi1, Gianfranco Magni1, Francesca Altieri1, Valeria Cottini3, Nicolas Gorius4, Patrick Gaulme5, François-Xavier Schmider6, Alberto Adriani1, Giuseppe Piccioni1 (1) Institute for Space Astrophysics and Planetology INAF-IAPS, Italy. (2) Center of Studies and Activities for Space CISAS, University of Padova, Italy. (3) University of Maryland, USA. (4) Catholic University of America, USA (5) New Mexico State University, USA (6) Laboratoire Lagrange, Observatoire de la Côte d'Azur, France Supporters list Roberto Orosei (INAF/IAPS, Italy), Giovanna Rinaldi (IAPS-INAF, Italy), Ernesto Palomba (IAPS-INAF, Italy), Alessandra Migliorini (IAPS-INAF, Italy), Maria Cristina De Sanctis (IAPS-INAF, Italy), Emiliano D'Aversa (INAF/IAPS, ITALY), Fabrizio Oliva (IAPS- INAF, Italy), Anna Milillo (INAF-IAPS, Italy), Agustín Sánchez-Lavega (Universidad del País Vasco UPV/EHU, Spain), Yves Langevin (Institut d'Astrophysique Spatiale, France), Patrick Irwin (University of Oxford, United Kingdom), Joern Helbert (DLR, Germany), J.-C. Gerard (LPAP- Univ. de Liege, Belgium), Rumi Nakamura (IWF/OEAW, Austria), Bortolino Saggin (Politecnico di Milano, Italy), Bianca Maria Dinelli (ISAC-CNR, Italy), Nikolay Ignatiev (Space Research Institute of Russian Academy of Sciences, Russia), David Luz (CAAUL/University of Lisbon, Portugal), Ioannis A. Daglis (Department of Physics - University of Athens, Greece), Glenn Orton (Jet Propulsion Laboratory- California Institute of Technology, USA), Alexander Rodin (Moscow Institute of Physics and Technology, Russia), Themelis Konstantinos (National Observatory of Athens, Greece), Britney E Schmidt (Georgia Institute of Technology, United States), Thomas B. McCord (Bear Fight Institute, USA), Randy Gladstone (SwRI, USA), H. MAVROMICHALAKI (University of Athens, Greece), anna maria fioretti (CNR - Institute of Geosceinces and Earth Resources, Italy), Kurt Retherford (Southwest Research Institute, USA), Michael Davis (Southwest Research Institute, United States of America), Bertrand Bonfond (Université de Liège, Belgium), Iannis Dandouras (IRAP, France), Dario De Fazio (IMIP-CNR, Italia), Leo Girardi (INAF - Osservatorio Astronomico di Padova, Italy), Tiziano Maestri (University of Bologna, Italy), Mauro Focardi (INAF-OAA, Italy), Jean-Baptiste Vincent (MPS, Germany), Neil Murphy (Jet Propulsion Lab, US), Mark Hofstadter (JPL/Caltech, United States), Anna Cinzia Marra (CNR-ISAC, ITALY), Vincenzo della Corte (Università degli Studi di Napoli Parthenope, Italy), Arnold (DLR, Germany), Gian Paolo Marra (CNR-ISAC , ITALY), Maurizio Pajola (CISAS - University of Padova, Italy), Maarten Roos (Lightcurve Films, Portugal), Cesare Grava (Southwest Research Institute, USA), and many others (see ODINUS website for the full list). ODINUS website and full list of supporters http://odinus.iaps.inaf.it/ 2/20 The ODINUS Mission Concept Overview The planets of our Solar System are divided in two main classes: the terrestrial planets, populating the inner Solar System, and the giant planets, which dominate the outer Solar System. The giant planets, in turn, can be divided between the gas giants Jupiter and Saturn, whose mass is mostly constituted by H and He, and the ice giants Uranus and Neptune, whose bulk composition is instead dominated by the combination of the astrophysical ices H2O, NH3 and CH4 with metals and silicates. While in the case of the gas giants H and He constitutes more than 90% of their masses, in the case of the ice giants these gaseous envelopes are more limited, amounting to only 1-4 Earth masses (De Pater and Lissauer 2010). The terrestrial planets and the gas giants have been extensively studied with ground- based observations and with a large numbers of dedicated space missions. The bulk of the data on the ice giants, on the contrary, has been supplied by the Voyager 2 mission, which performed a fly-by of Uranus in 1986 followed by one of Neptune in 1989. The giant planets appeared extremely early in the history of the Solar System, forming across the short time-span when the Sun was still surrounded by a circumstellar disk of gas and dust and therefore predating the terrestrial planets. The role of the giant planets in shaping the formation and evolution of the young Solar System was already recognized in the pioneering works by Oort and Safronov in 1950-1960. In particular, Safronov (1969) suggested that the formation of Jupiter would inject new material, in the form of planetesimals scattered by the gas giant, in the formation regions of Uranus and Neptune. More recently, the renewed understanding of planetary formation we obtained by the study of extrasolar planetary systems gave rise to the idea that the Solar System could have undergone a much more violent evolution than previously imagined (e.g. the Nice Model for the Late Heavy Bombardment, Tsiganis et al. 2005), in which the giant planets played the role of the main actors in shaping the current structure of the the Solar System. The purpose of this document is to discuss the scientific case of a space mission to the ice giants Uranus and Neptune and their satellite systems and its relevance to advance our understanding of the ancient past of the Solar System and, more generally, of how planetary systems form and evolve. As a consequence, the leading theme of this proposal will be the first scientific theme of the Cosmic Vision 2015-2025 program: ● What are the conditions for planetary formation and the emergence of life? In pursuing its goals, the present proposal will also address the second and third scientific theme of the Cosmic Vision 2015-2025 program, i.e.: ● How does the Solar System work? ● What are the fundamental physical laws of the Universe? The mission concept we will illustrate in the following will be referred to through the acronym ODINUS, this acronym being derived from its main fields of scientific investigation: Origins, Dynamics and Interiors of Neptunian and Uranian Systems. As the name suggests, the ODINUS mission is based on the use of two twin spacecraft to perform the exploration of the ice giants and their regular and irregular satellites with the same set of instruments. This will allow to perform a comparative study of these two systems so similar and yet so different and to unveil their histories and that of the Solar System. 3/20 The ODINUS Mission Concept Theme 1: What are the conditions for planetary formation and the emergence of life? In this section we will briefly summarize how our understanding of the processes of planetary formation has evolved across the years, discuss their chronological sequence for what concerns the Solar System and highlight how the exploration of Uranus, Neptune and their satellite systems can provide deeper insight and better understanding of the history of the Solar System. The Evolving View of Planetary Formation: Solar System and Exoplanets The original view of the set of events and mechanisms that characterize the process of planetary formation (Safronov 1969) was derived from the observation of the Solar System as it is today. This brought to the assumption that planetary formation was a local, orderly process that produced regular, well-spaced and, above all, stable planetary systems and orbital configurations. However, with the discovery of more and more planetary systems through ground-based and space-based observations, it is becoming apparent that planetary formation can result in a wide range of outcomes, most of them not necessarily consistent with the picture derived from the observations of the Solar System. The orbital structure of the majority of the discovered planetary systems seems to be strongly affected by planetary migration due to the exchange of angular momentum with the circumstellar disks (see e.g. Papaloizou et al. 2007 and references therein), in which the forming planets are embedded, and by the so-called “Jumping Jupiters” mechanism (Weidenschilling & Marzari 1996; Marzari & Weidenschilling 2002), which invoke multiple planetary encounters, generally after the dispersal of the circumstellar disk, with a chaotic exchange of angular momentum between the different bodies involved. The growing body of evidence that dynamical and collisional processes, often chaotic and violent, can dramatically influence the evolution of young planetary systems gave rise to the idea that also our Solar System could have undergone the same kind of evolution and represent a “lucky” case in which the end result was a stable and regular planetary system. The most successful attempt to describe the evolution of the Solar System to the present epoch has been the so-called Nice Model (Gomes et al. 2005; Tsiganis et al. 2005; Morbidelli et al. 2005; Morbidelli et al. 2007; Levison et al. 2011). The Nice Model is a Jumping Jupiter scenario formulated to link the event known as the Late Heavy Bombardment (LHB, see e.g. Hartmann et al. 2000 for a review) to a migration event involving all the giant planets. In the Nice Model, the giant planets of the Solar System are postulated to be initially located on a more compact
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    The Science Return from Venus Express Venus Express Science Håkan Svedhem & Olivier Witasse Research and Scientific Support Department, ESA Directorate of Scientific Programmes, ESTEC, Noordwijk, The Netherlands Dmitri V. Titov Max Planck Institute for Solar System Studies, Katlenburg-Lindau, Germany (on leave from IKI, Moscow) ince the beginning of the space era, Venus has been an attractive target for Splanetary scientists. Our nearest planetary neighbour and, in size at least, the Earth’s twin sister, Venus was expected to be very similar to our planet. However, the first phase of Venus spacecraft exploration (1962-1985) discovered an entirely different, exotic world hidden behind a curtain of dense cloud. The earlier exploration of Venus included a set of Soviet orbiters and descent probes, the Veneras 4 to14, the US Pioneer Venus mission, the Soviet Vega balloons and the Venera 15, 16 and Magellan radar-mapping orbiters, the Galileo and Cassini flybys, and a variety of ground-based observations. But despite all of this exploration by more than 20 spacecraft, the so-called ‘morning star’ remains a mysterious world! Introduction All of these earlier studies of Venus have given us a basic knowledge of the conditions prevailing on the planet, but have generated many more questions than they have answered concerning its atmospheric composition, chemistry, structure, dynamics, surface-atmosphere interactions, atmospheric and geological evolution, and plasma environment. It is now high time that we proceed from the discovery phase to a thorough